The present invention relates to a regulating device for handling a needle thread from a tension device to a needle to loosen a thread and to absorb looseness of a thread in a multi-needle double chain stitch sewing machine. In the present invention, the needle thread is arranged in plural sets corresponding to the needles.
Japanese Patent No. 2974557 discloses this kind of regulating device, in which said needle thread is controlled by the vertical motion of the needle bar take-up, and cam face action of the thread handling plate, so as to loosen the thread or absorb thread looseness. This regulating device comprises a needle bar take-up and a thread handling plate. The needle bar take-up is supported by a needle bar, and moves up and down together with the needle bar. The needle bar take-up is stuck out of a through-hole opened in the sewing machine head. The thread handling plate is disposed at the front side of the sewing machine head near the through-hole, and has a cam face extending in the vertical direction. The tension device has plural thread tensioners.
In this regulating device, the cam face of the thread handling plate comprises a cam face portion for the left needle thread and a cam face portion for the right needle thread, with the respective cam face portions formed before and after the thread handling plate. Each cam face portion is designed to absorb the needle thread loop that is formed when the needle is slightly lifted from the lowest position. Consequently, the looper picks up and tightens the needle thread.
In the multi-needle double chain stitch sewing machine, as shown in FIG. 4, needles 8 are arranged in the lateral direction, and the looper 7 moves in the lateral direction to sequentially pick up the needle thread loop 8L of each needle 8 from the right side. In order to match the timing of each needle 8 with the looper 7, the height of the needle hole is set gradually lower on the left side of the needle. Therefore, for the leftmost side of the needle, the needle ascending distance from the lowest position is the longest at a pick-up position of the needle thread loop by the looper. Consequently, the needle thread loop that is formed as the cloth is handled during the ascending motion of the needle is also large. If the needle thread loop is too large, the needle thread loop may collapse, and the looper may fail to pick up the needle thread loop.
In the regulating device disclosed in Japanese Patent No. 2974557, as shown in FIG. 5, during the ascending motion of the needle bar take-up, the left needle thread t slides along the cam face c in the direction of the arrow to reach point a (this point is right after the looper picks up the needle thread loop). In this manner, the regulating device is designed to absorb the looseness of the needle thread loop by the cam face c. However, since the gradient and rise L of the cam face c are large, it is difficult to slide the needle thread t smoothly along the cam face c.
In this regulating device, the needle bar take-up sticks out of the front side of the sewing machine head. The needle thread is passed through a plurality of eyelets that are formed at the leading end of the needle bar take-up and which are arranged in the longitudinal direction, while the cam faces are formed side by side before and after the needle handling plate. Accordingly, the extent of the needle bar take-up and thread handling plate that sticks out of the sewing machine head front side toward the operator is increased, thereby creating a threatening pressure to the operator. Additionally, a plurality of cam faces are formed in the thread handling plate, resulting in an even more complicated structure. Moreover there are lubricating points on the bearing that supports the needle bar and the upper shaft, along with other lubricating points in the sewing machine head, and during vertical motion of the needle bar or rotation of the upper shaft, the lubricating oil may splash outside through the through-hole in which the needle bar take-up sticks out.
It is hence an object of the invention to present a regulating device for handling a needle thread in a multi-needle double chain stitch sewing machine capable of moving the needle threads smoothly by minimizing the rise of the cam face engaged with the needle thread, from the time of the needles ascending via the lowest position until the threads is tightened right after the looper picks up the needle thread loops. It is other object to present a regulating device for handling a needle thread in a multi-needle double chain stitch sewing machine simplified in structure by forming only one cam face in the thread handling body, lessened in the threatening pressure by reducing the stuck amount of the thread handling body and thread taking-up tool to the operator, and free from splash of oil to outside of the sewing machine.
The present invention comprises a thread taking-up tool and a thread handling body. The thread taking-up tool is attached to the needle bar, and moves vertically together with the needle bar, and a plurality of thread holes are formed at its leading end. The thread handling body is attached to the front side of the sewing machine head near the thread taking-up tool, and has a cam face extending in the vertical direction. Loosening of needle thread and absorption of its looseness from the tension device to the needle are executed by the vertical motion of the thread taking-up tool and the cam face action of the thread handling body.
It is a first feature of the present invention that thread hooking means is provided in the thread taking-up tool. The thread hooking means is engaged with the needle thread supplied to the remotest needle where a largest needle thread loop is formed, among the needles arranged in the lateral direction. The thread engagement of the hooking means is continued until the looper picks up the needle thread loops as the needle ascends from the lowest position between the thread holes of the thread taking-up tool and the cam face of the thread handling body. By engagement of the thread hooking means, other needle thread is took up with the remotest end needle thread staying at the curved lower end of the cam face.
According to the present invention, looseness of the needle thread loop in the needle at the remotest end where a largest needle thread loop is formed is absorbed by ascending the thread hooking means and the thread taking-up tool with the needle thread staying at the lower end of the cam face. In other words, looseness of this thread loop is absorbed as the needle thread from the lower end of the cam face to the needle is lifted by the thread taking-up tool and the thread hooking means. Moreover, until the looper picks up the needle thread loops, said needle thread remains at the lower end of the cam face. That is, until the looper picks up the needle thread loops to tighten the thread, said needle thread does not slide on the cam face, and cam action is not effected, and hence, the cam face is shorter, the cam rise is smaller, and sliding of needle threads on the cam face is smaller, so that sliding on the cam face is smoother.
The thread hooking means used in the present invention is structured so as to take up other needle thread while the left needle thread is remaining at the cam face lower end until the looper picks up the needle thread loops, and to carry out the handling action of the needle thread. An example is shown as an endless hook in a preferred embodiment below.
It is also a feature of the present invention that the thread taking-up tool is attached to a portion of the needle bar sticking out from the sewing machine head, and that the plurality of thread holes at the leading end of the thread taking-up tool are arranged in the lateral direction.
According to the invention having such structure, by attaching the thread taking-up tool to the needle bar outside of the sewing machine head, it is not necessary to form a through-hole for the thread taking-up tool in the sewing machine head. Accordingly, oil does not splash out from the through-hole formed in the conventional sewing machine head for allowing the thread taking-up tool to stick. Moreover, since the thread holes are formed in the lateral direction, as compared with those formed in the longitudinal direction, the stuck extent of the thread taking-up tool from the sewing machine head to the operator side is smaller.
In a preferred aspect of the invention, the thread taking-up tool is provided at the needle bar sticking out from a position obliquely drawn back in the lower part of the sewing machine head.
Since the lower part of the sewing machine head is usually in a obliquely drawn back shape, when the thread taking-up tool is provided at the needle bar sticking out from the sewing machine head, the thread taking-up tool is also drawn back, being close to the slope drawn back in the lower part of the sewing machine head. As a result, as compared with the structure of sticking out of the front side from the through-hole of the sewing machine head, the stuck extent to the operator is smaller, and the threatening pressure to the operator can be lessened.
In another preferred aspect of the invention, one cam face is formed on the thread handling body, and a plurality of needle threads are engaged with the one cam face.
According to the invention having such structure, since only one cam face is enough, the structure of the thread handling body is simple, and the stuck extent of the thread handling body is smaller.
In a further preferred aspect of the invention, the preferred or other preferred aspect of the invention is combined with the first aspect of the invention. As a result, effects by combinations of aspects of the invention are brought about.